This is interesting but your numbers for taxes and health care are too inflated. Someone making $115k will likely have an effective tax rate of around 17%. Someone making $300k will likely have an effective tax rate of around 22%. The latter will still take home more than twice as much before factoring in retirement & health insurance. And I don't know anyone paying $32k per year for health insurance and other costs. Most Americans don't even bring home that much money.

The thing I find most interesting (and troubling) is that developers can get trapped in a situation where they can no longer bump their salary if they switch jobs. Or worse, when they don't have the current tech stack experience to even stay at their current level and have to accept less.